Graving dry dock and method of construction



Ja n. 4, 1944. 1 F. R. HARRIS 2,338,110

GRAVING DRYDOCK AND METHOD OF CONSTRUCTION Filed Dec. 9, 1940 -2 Sheets-Sheet 1 1 f1 a- V WITNESSES Q INVE TOR 1 Y k I Jan. 4, 1944. F. HARRIS GRAVING DRYDOCK AND METHOD OF CONSTRUCTION 2 Shets-Sheet 2 Filed Dec. 9, 1940 INKENTOR WITNESSES Patented Jan. 4, 1944 I OFFICE GRAVING DRY DOCK AND METHOD OF CONSTRUCTION" Frederic E. Harris, New York, N. Y. Application December 9, 1949,. Serial No. 369,266

5 Claims.

My invention refers to a method and to a'combination of structural elements whereby the building of large graving docks is materially reduced in time and cost, and my invention sometimes makes it practical to construct a basin dock in localities where local conditions are such as to prohibit the building of such a clock by the present conventional methods;

In large graying docks,water of considerable head must be excluded, and for that very reason the character of the sub-soil and foundations are of considerable importancein locating structures of this type.

Graving docks have been constructed in unstable water bearing soils, but at high cost.

In certain localities it is'impossible or impracticable, within the range of ready execution, to construct graying docks by any methods involving the unwatering of the site.

When such cases occur, resource mustbe had tova method of construction that will make the unwatering of the site unnecessary.

With the increase in draft of vesselsiand the necessity for providing overdraft in case of accident; the clearance depth over the sills of graving docks has increased and with it the increase in the head of ground or sea water to be taken care of during the construction period. I

New methods must therefore be devised to meet the added requirements and my invention refers.

to a methodanda combination of old elements, whereby the building of large graying docks in localities that forbid the use of unwatering of the site during the construction period, may be eX- peditiously undertaken without raising the cost thereof to the prohibitive figure of the present conventional methods.

Therefore, as my invention involves the use of a combination of old elements through which a newand useful result is achieved, I do not only lay claim to the combination shown butalso to the several necessary steps of my method as part of my invention.

In the drawings, Figure-1 is a fractional plan view showing the inshore end of my preferred skeleton structure placed in the unwatered dock site'excavation, and Figure 2 showsa similar plan view of the outshore end thereof.

Figure 3 is a cross section of the dock site excavation showing the entrance end of the skele ton structure therein, the section being taken on the line 3'-3-of Figure 2; and Figure 4 shows the wet-as well as the dry concret work -in place in my preferred dry dock construction.

In the drawings where like reference characters designate corresponding parts, I denotes the dock site excavation in which are located steel trusses 2 for supporting and'reinforcing sheet metal partitions t that are used in the construction of a tremie concrete bottom 3.

'The transverse partitions 4 are attached to the trusses 2, and these partitions are preferably made out of sheet iron provided with relatively deep vertical corrugations ll.

The side partitions 4 are shown clamped to the ends of two adjacent transverse trusses 2 by means of the side battens 2' so that a unit form pocket i3 is formed, inside'of which tremie concrete may be confined.

As shown in Figures 1 and 2, I prefer to continue the side partitions 4' out beyond their respective form pockets l8, so that the series of form pockets it will alternate with a series of form pockets it, all as shown in the drawings. I have discovered that by making the form pockets relatively narrow, say some 12 to'l5 feet, tremie concrete may be poured therein without the concrete being damaged before it sets. Also the use of deep vertical corrugations ii in the transverse partitions causesa most eifective shear bond, resulting from the greatly increased adherence surface, as well as from the interlocking serrations between adjacent trernie concrete masses.

It is to be'noted in this connection that the weight of the side walls which span the ends of the blocks prevents any uplift of the block ends, while the middle portion of the bottom tends to rise when the dock is unwatered.

This uplift is resisted by the ship load, but as this load varies considerably over the length of the ship, especially if the ship hull is damaged, it is of prime importance that the bottom shall ct as a single monolithic structure, so that any concentrated load excess unit will be properly distributed over a considerable surface.

The inclusion of side bracing of the wing walls in my combination of elements, similarly causes any local earth pressure excess on the sides both duringand after constructionto be transmitted into a large and expansive bottom area.

Close to the ends of the steel trusses 2 I prefer for water tightness and for proper bearing support of the tremie concrete.

Similarly across the inner end of the dry dock site proper end braces 8 are provided.

The inshore end of a graving dock is known as the head, as distinguished from the outshore end, or entrance.

Heads are sometimes built rectangular, as shown in my construction, but the shape of the head may be trapezoidal, circular or elliptical with the end bracing conforming to the general outline thereof.

At the entrance end of the dock site I prefer to drive a temporary conventional interlocking sheet piling 9 and support it by temporary bracing In, similar to the side bracing 5 and I show it connected to my preferred truss reinforcing of the tremie concrete bottom slab. Similar sheet piling 9 braced by the parts ii is placed at the inshore or head end.

Backfill II is preferably put in place after the setting of the tremie concrete and prior to the unwatering of the dock structure. A temporary partition wall 53, the construction of which is similar to the side piling i, is preferably built near the entrance end of the dock so that a dock basin will be formed which may be readily pumped out.

The dry concrete work I2 is put in place after the unwatering of the dock basin 2!] and in it the suction duct l3 and discharge duct [4 are built, and a gate seat i5 (Figure 2) is constructed at the entrance end of the dock so as to accommodate a regular pontoon steel gate id as indicated by the dash dotted lines in the drawings.

My preferred method of construction is as follows:

After the site of the graying dock has been selected, the necessary excavation is undertaken and a layer of gravel fill 22 is placed on the dredged bottom.

Piling 23 is driven and I prefer to cut the piles so that the pile ends project some three feet out of the gravel fill.

The unit form pockets 18 are lowered in place and tremie concrete is poured first into the center pockets i8, whereupon the pockets H) are filled with tremi concrete.

I prefer to deposit the tremie concrete by means of large diameter pipes, through which placer pipes the tremie concrete is poured continuously until a unit form pocket is filled.

When the trernie concrete bottom has properly set, I have a basin 2% comprising in combination a rigid continuous heavy bottom slab conforming in width and height with the unit form pockets, and this bottom slab is substantially surrounded by water-ti ht interlocking sheet piling, braced to and supported by the bottom slab itself.

Backfill l i is now dumped in against the sheet piling to insure water-tightness, whereupon the entire basin is unwatered and the permanent dry concrete work is built in the unwatered basin.

It is to be noted that the water pressure exerted on the side walls is taken up by the side bracing, and that the bottom pressure is being counteracted by the weight of the side walls as well as the weight of the tremie concrete slab in the unwatered dock basin.

It is also to be noted that where the depth of the dock is relatively great, the bottom tremie concrete block between the wing walls thereof may be preferebly poured first whereupon the side walls maybe poured in one operation between the bottom of the site up to a point say 15 to 30 feet above the top of the tremie concrete bottom slab and in such cases I prefer to place the side wall bracing on top of the side wall tremie concrete blocks.

It is to be noted that the side walls of the graving dock are built up around the side steel bracing 5 which is so designed as to allow the passage of pump culverts and ducts for piping, wiring, and so forth.

At the entrance end of the dock proper seating for a conventional dock gate pontoon is provided in the dry concrete work and when the work is completed, the dock basin is flooded and the temporay partition wall 9 at the entrance of the dock is pulled out and removed, and the dock is ready for operation.

I do not wish to be understood as limiting my claims to the structure shown as it is evident that alterations and modifications may be made in my device without departing fom the scope and spirit of my invention.

I claim:

1. The method of constructing a basin dry dock in a water bearing soil, characterized by excavating the site, placing a series of truss-reinforced, sheet metal partitions, in general parallel relation across the bottom of the excavation and with the partitions spaced from one another to form walls of relatively narrow unit form pockets, and with other partitions connected to the ends of the transverse partitions to complete said form pockets, connecting sheet piling to the form pockets all around the excavation with the sheet piling extending upward from the form pockets, bracing the sheet piling, filling the form pockets with tremie concrete and placing backfill against the sheet piling so as to form a substantially watertight basin, unwatering the basin and placing dry concrete therein to form the side walls of the dry dock.

2. The method of constructing a substantially monolithic dry dock bottom under water, characterized by constructing a series of narrow, open-bottom form pockets side by side on the dock site before pouring the concrete and separating each form pocket from the next adjacent form pocket on each -side by a single truss-reim forced vertically-corrugated partition extending transversely of the space on which the dry dock bottom is to be constructed, and filling the form pockets with tremie concrete to form a bottom slab made up of portions interlocked with a toothed bond formed by the corrugated faces of adjacent portions on opposite sides of the partitions.

3. In the construction of a basin dry dock, the method that comprises placing reinforced sheet metal partitions in positions to provide forms for the dry dock bottom under water on the selected site of the dry dock, spacing the forms in such relation that they provide relatively narrow adjacent pockets each of which is separated from the next only by a thickness of one of said sheet metal partitions, supporting a continuous partition wall with the top of said wall above the water level at said site and the lower end of said wall extending into the bottom forms and below the top level of said forms around the entire edge region of the space that is to be occupied by the dry dock bottom, constructing the bottom by filling the bottom forms with tremie concrete to a level over the sheet metal reinforcing and above the lower end of the wall, after the concrete has set, removing the water from the space above the bottom and within the partition wall, and constructing the side walls of the dock within the dry space thus provided.

4. A dry dock structure comprising a series of relatively narrow form pockets made up of generally parallel, truss-reinforced, sheet metal partitions extending across the dock site for holding the concrete for the bottom of a dry dock, each of said partitions including a skeleton frame and sheet metal that is vertically corrugated to provide concrete interlocking teeth on the adjacent sections of the concrete bottom, and battens holding the partitions in spaced relation with respect to one another. I

5. A dry dock structure comprising a concrete bottom that is supported by the ground at the site of the dry dock, sheet piling side walls extending all around the bottom and embedded in the concrete of, the bottom along their lower edges, said side walls extending from the bottom to a level above the Water at said site, and skeleton frames including beams that are anchored in the concrete bottom and connected together above the bottom to form a number of spaced trusses along the length of the side walls, each of said trusses extending inward from the side walls for holding a said side walls against lateral pressure of earth or water around the dry dock structure.

FREDERIC R. HARRIS. 

